Dynamic behavior of a transmembrane molecular switch as an artificial cell-surface receptor

Supramolecular functions of a novel synthetic amphiphile with an azobenzene core interposed between two aminoalkyl chains as an artificial transmembrane receptor were investigated. Hybrid vesicular membrane was prepared in combination with the receptor and a bilayer-forming lipid dimyristoylphosphatidylcholine (DMPC). Aggregation behavior of the receptor embedded in the bilayer membrane was evaluated spectrophotometrically by monitoring stacking of the azobenzene moiety. Upon addition of 1-hydroxy-2-naphthaldehyde as an external signal ligand, it was effectively recognized at both ends of the receptor by forming the corresponding Schiffʹs base, and followed by phase reorganization of the receptor in the membrane. The resulting receptor–ligand complex provided an appropriate binding site for copper(II) ions, which may act as a second messenger signal. Signal transduction behavior of the present supramolecular system was examined by employing NADH-dependent lactate dehydrogenase (LDH) as an effector. We found that the transmembrane receptor is capable of performing as a molecular switch for the enzymatic reaction.